Astrology tells us not what we are doing for a living, but what we are supposed to be doing. Your money houses are the second, eighth and eleventh and planets there are clues, also aspects to the midheaven. The fifth house rules creativity, so the sixth house represents money made from creative projects. I have no planets in the 6th, which I suppose means I will never make a living writing books. I don't stop writing or trying to publish because of it though. The fact is that a chart is never simple nor easy to understand and there are exceptions to every rule. That doesn't make astrology untrue, like heaven above us we don't understand it, that's all.
It is a fact that we enjoy doing what we are supposed to do, so Venus the planet of what pleases us is a clue to career. My Venus is in the 12th house, which means I enjoy solitude and working alone. (Sounds like a writer to me) Venus also quintiles the midheaven. Mercury, the planet of communications trines my midheaven. (120 degrees away) My midheaven is in Virgo, but as Virgo obsesses (usually about their health, this is the sign of the hypochondriac) astrologers say that a Virgo midheaven might only mean that you are obsessed by your career. The element of the sign at the midheaven is a very important clue to oneself, a earth sign wants to see real results for their efforts, an air sign might work just for the mental challenge, a fire sign might work just for spiritual rewards or to be a leader and in the spotlight, a water sign wants an emotional tie to their career as water signs are all about their emotions. Virgo is earth, and the biggest thrill of my life is seeing my name on something I've written or a check for something I wrote. To be paid money for what I write means that it has value, and the money I've made writing means more to me than any other money I've ever made.
For me the biggest clue was Neptune, the planet of dreams in the 11th house. The 10th represents career, so the next house is money made from your career.
A writer could be called someone who makes money from their dreams.